Two of the families who lost sons in the RAF Nimrod that burst into flames over Afghanistan two years ago, killing all 14 people on board, will begin a landmark damages suit against the Ministry of Defence in the High Court today.

Their case will focus on alleged MoD negligence in failing to ensure that the Nimrod was safe to fly. The aircraft blew up during mid-air refuelling when fuel leaking through a corroded coupling in pipework ignited after coming into contact with a hot-air pipe. Andrew Walker, the assistant deputy Oxfordshire coroner, concluded at the inquest into the 14 deaths in May that the Nimrod surveillance aircraft had never been airworthy because of a fundamental design fault.

John Cooper, a barrister acting for the families of Sergeant Benjamin Knight, 25, and Flight Lieutenant Steve Swarbrick, 28, both of 120 Sqadron, RAF Kinloss, Morayshire, will issue a writ for compensation, based on alleged negligence, failure of duty of care to the personnel who were killed and a breach of their right to life under Article 2 of the European Convention on Human Rights.

Mr Cooper said that if the two families were to win their case against the MoD, they felt that it would have repercussions not only for all the Nimrod families but also for other cases where it was alleged that the ministry had failed to provide adequate equipment for service personnel in Afghanistan and Iraq.

Graham Knight, the father of Sergeant Knight, told The Times: “My son and 13 others were killed and not one person has been held accountable for it. The Government has said they are very sorry, but sometimes sorry isn't enough. We want to know who was responsible for airworthiness and what has happened to them. I have seen a lot of medals being handed out, but nobody seems to have been held accountable. We want to prevent anything like this happening again.”

Mr Cooper said: “The view of the families is that the MoD should be accountable for providing shoddy equipment. They say the design of the Nimrod was flawed and that there was no fire-suppressant foam fitted to the aircraft. They also say that it wasn't as if the Nimrod was engaged in combat at the time — it was just being refuelled.”

The families' writ states that the MoD was in breach of its responsibilities under the Safety of Work Act 1974 by failing to reduce known risks facing the crew of the Nimrod, codenamed XV230. At the inquest into the 14 deaths, Mr Walker accused the MoD of a “cavalier approach” to safety. He also called for all 15 of the RAF's Nimrods to be grounded. This was rejected by the MoD after Air Chief Marshal Sir Glenn Torpy, the Chief of the Air Staff, declared that the aircraft was safe to fly. Since the disaster on September 6, 2006, the close proximity of hot-air pipes to fuel pipes has been addressed, and mid-air refuelling has been suspended.

Mr Cooper told The Times: “If people had died on board a commercial aircraft flying home from their holidays then there would have been not only resignations but also inquiries.”

The MoD commissioned an inquiry by Charles Haddon-Cave, QC, into the circumstances that led to the crash.It is still under way. An MoD spokeswoman said yesterday: “We cannot comment on a potential lawsuit.”

A separate investigation by QuinetiQ, the MoD's former defence research agency, found that some safety features had been left out of the design specification for Nimrod surveillance aircraft despite being requested by the RAF. It also found that the number of maintenance specialists at RAF Kinloss had been cut by nearly 24 per cent and that many workers were inexperienced with Nimrods.

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